in this town of glass and ice
by Mia-Zeklos
Summary: When Alec and Jace's parabatai bond first starts changing, Sebastian takes interest in exploring it further.
1. Chapter 1

**Notes: I've had this idea running around in my head for a while and it wouldn't leave me alone, so I decided to give it a try despite how obscure the concept turned out to be. Canon events, while present to some degree, are barely mentioned so the timeline shouldn't be too difficult to catch up with. I'm planning on actually delving deeper into details around the magic and everything surrounding it in the next chapter; this is meant to serve mostly as introduction.**

If Jace was honest with himself, he had to admit that he wasn't really surprised by Sebastian's request. Really, it had been a long time coming and while Jace knew that Alec was right and that they had to be extremely careful, it had been _months_. Sebastian had more than earned their trust already and it didn't feel right to keep him in the dark about something so crucial – not when it could potentially affect him too.

"If you want to keep it between you and Alec, that's fine by me." The lengthy silence had been a clear enough proof of Jace's doubt, he suspected, because Sebastian had spoken up again. "It's something very private, after all. It's just– my father had a parabatai. Things didn't end well between them – his parabatai betrayed him – and he didn't talk about it much, but he studied other bonded pairs sometimes."

"Your father was a scholar?" Jace could count the times Sebastian had mentioned his family on the fingers of one hand and it was almost always used as a justification of some sort. That seemed to be the case now too; even when he was like this, relaxed and still half-asleep, the thought was apparently never far from his mind.

"Not at all." There was a hint of a smile to his voice and, sensing the strain in it, Jace carded his fingers through Sebastian's hair just to remind him that he was there. It was far too easy to get lost in memories; he knew that better than anyone, even if he didn't know that Sebastian knew that he was safe now. He Sebastian had a room at the Institute already, but he still favoured his flat above that and Jace didn't have it in him to complain. It made for a perfect meeting place even if it meant that Alec had to live before dawn sometimes to get to the Institute in time. "But he had his– fixations. And he believed that, if the relationship between parabatai turns into a romantic one – if it's consummated – then it can generate angelic power much stronger than the one used for tracking. I was just wondering if he was right."

There wasn't much that Jace knew about Sebastian's father. He'd left years ago, that much he was sure of, when Sebastian had still been a child, which was enough to explain his endless curiosity about the things the man had been interested in. And really, with that in mind, Jace could imagine turning him away; not for something that still fascinated him and Alec just as much.

 _Can I see your magic?_ The question had been accompanied by a casual enough tone for Jace to know that Sebastian was doing his best to remain nonchalant and the thought brought a smile to his face as he raised his hand until it was in his lover's field of vision. With the slightest bit of concentration, he let the power that coursed in his blood – the one that both he and Alec had finally learnt to rein in – crack through his fingers, illuminating the bedroom with its dark red glow.

 **o.O.o**

It hadn't always been like this. If someone had told Jace just a few months ago that he would be comfortable enough with someone to share with them the details of his and Alec's bond, he would have laughed in their face. It wasn't something either of them had even considered discussing before – it was far too intimate and far too dangerous all at the same time, given the nature their relationship had had for quite a while now – and it was best kept behind closed doors.

It was just one of the many reasons why he and Alec had been terrified when Sebastian had first found out about them. It had happened in the most ridiculous way, too; there had been a red alert of some sort in the Institute and they had been nowhere to be found, so the man – who, as Alec had pointed out more than once, took his job very seriously – had tracked them down to the hotel where they'd been staying for the night. He'd told them later on that he'd almost brought a search party, and Jace didn't even want to think of what would have happened _then_. As it was, he could only be grateful that Sebastian had listened to reason when Alec had asked him (begged, almost, although Jace was the only one who knew him well enough to see the desperation in his eyes) to keep it to himself.

"I think it's cruel," Sebastian had said then, laying a comforting hand on Alec's forearm to keep him in place, "what the Clave is doing to you. To let two people enter such a powerful bond and to force them to stay apart is unthinkable."

"You have a parabatai?" Some of the tension from before had lessened along with the firmness of Alec's grip on Sebastian's arm. The change had been almost imperceptible, but still enough for Jace to notice. Sebastian had shaken his head.

"No, but I've heard the stories. The parabatai bond is one of a kind, and for it to be restrained like this... it's a crime."

Over the next week or so, Alec and Jace had come to the wordless agreement that one of them had to be aware of every step Sebastian made and they'd split this new duty equally between themselves in the silent hope that they were inconspicuous enough. If Sebastian had noticed, he hadn't said anything and, to their relief, he hadn't told anyone anything else either.

Slowly, Jace had started trusting him. He'd appeared to be too passionate about their case to actually do anything to bring their relationship to light and, if anything, he was _helping_ – their lives had become significantly easier since Alec had trusted him with the Institute's security. It had been the first sign that Alec had started to give in too and Jace had been irrationally satisfied by that. It was easier to bear the secret now that they had someone to share it with – someone who had only made things better so far – and without fully realising it, they'd both started confiding in Sebastian much more often.

How Sebastian had become part of their relationship was a whole other story; one complicated enough that sometimes Jace still couldn't tell for sure when it had started. All he knew was that at one point his interest in Sebastian had morphed into something suppressing friendship and when Alec had detected that, he'd cut Jace off in the middle of his frantic apology to admit that he felt the same way. From then on, it had seemed like they only had one course of action to follow.

They'd decided to be as open as possible from the very beginning, the three of them, but even now Sebastian was still a bit of a mystery for both him and Alec. It wasn't especially surprising – he wasn't connected to them the way they were to each other – and so they'd tried to include him in all the changes in their bond as soon as they happened. Or at least, Jace had. It was taking a while longer for Alec and as much as Jace tried to speed up the process, he knew his parabatai well enough to know that he was seeing this as a necessary precaution rather than actual distrust.

That, of course, didn't mean that Sebastian wasn't perceptive enough to notice.

"Alec would be charmed," he muttered as Jace fiddled with the candles on the other end of the room, the fire dancing with every little twitch of his fingers. "What else can you do?"

"He's got magic too," Jace said, distracted by the effort of keeping the flame under his control. "He's better at the mind reading than I am, though."

Sebastian stiffened under his touch. "Mind reading."

"It only works for me and we still don't share _every_ thought," Jace assured him. The edge to Sebastian's voice was exactly what he'd expected given the circumstances. "But if you _try_ and talk to him, he'll probably be able to hear you."

 _Can you hear me now?_

Jace laughed despite himself. While he had to admit that the changes in the bond worried him sometimes, they were worth it just for moments like this. "Yes."

"We can test it sometime, all three of us," Sebastian said. Jace could tell by his tone alone that he was already considering at least fifty ways in which this could be useful. "If we learn how to control it fully, it could be a great advantage. Does anyone else know?"

"No one." They hadn't even told Clary and Izzy yet because they hadn't wanted to worry them too much with these new changes when they were still so absorbed in trying to find Valentine. Sebastian was safe in that regard; while he was excellent at what he did, nothing – not even the war – seemed to really affect him. Jace didn't think he'd ever seen him upset. Most of his reactions were as contained as they could get and Jace had been around Alec long enough to get used to that, but it was still occasionally startling to realise just how _little_ he knew about Sebastian apart from what the man had decided to share with them.

One of the things he _did_ know was that Sebastian was an excellent strategist, though, so he'd already expected to hear his next offer by the time he made it. "We could try it out later in the Institute before we do anything else, then. Only if Alec's willing to, of course."

"Why wouldn't he be?" Retracting his magic from the various light sources around them, Jace disentangled himself from the covers and tried to hunt down his clothes from last night. "He wants to learn more about our magic too, so if anything could help..."

"It's _your_ magic," Sebastian pointed out. His smile was a bit more strained now, but he hadn't moved from his position on the bed, leaning back against the headboard and idly tracking Jace's movement around the room with his eyes. "I don't expect him to trust me with it completely."

"He does trust you."

Sebastian scoffed.

"He _does_ ," Jace persisted. "He's trusted you with much more before. Why would this be any different?" _He trusted you with me_. Jace didn't say it, but it was still all the proof he needed. Alec had taken a leap of faith when he'd first confided in Sebastian about their relationship and things had been getting steadily better since then and Jace knew that he wouldn't change his mind now unless he was given a reason to.

"Maybe you're right." Despite the uncertainty in his voice, Sebastian seemed excited by the prospect. "I'll talk to him later. There's some paperwork I need him to sign anyway."

"I'll be right behind you." Despite having duties much different from Alec's current ones, Jace found himself in his office often enough and he looked forward to getting there even more now that they'd made a decision. "This should be interesting."

"I _hope_ so," Sebastian said before following Jace's example and getting up to get ready for the day and, just by taking one look at him, Jace could already tell that whatever he'd planned wouldn't be just another quick experiment.

He didn't really mind, he realised. He and Alec had danced around the issue long enough; it had just taken Sebastian to bring it to the surface.

 **o.O.o**

In the past few weeks, Alec had got so used to having Jace talk to him in his mind that he barely registered it as something out of the ordinary when he heard Sebastian's voice instead.

It wasn't actually his _voice_ , of course. The feeling wasn't quite the same as when someone was talking to him out loud, but it was close enough; the sound of it richer with undertones that spoken words could never really achieve. Jace's thoughts - the one intended for him - were always quick and barely there; a passing moment that Alec had to concentrate on to grasp before they disappeared. The new presence felt more like a focused effort; sharp and crystal clear in a way that had become unmistakable ever since Sebastian Verlac had turned up in the New York Institute one evening several months ago.

Nevertheless, it felt peculiar; the intimacy of the feeling one that he couldn't quite describe and the sudden intrusion pulled him out of the daze he'd fallen into while looking over the maps of New York and its immediate surroundings that he'd been provided with.

 _For all we know, he might not even be in the city_.

Alec almost jumped in his seat, eyes darting around the office until he found Sebastian leaning against the doorframe. He was _smiling_ , too, clearly conscious of what he'd done, and Alec connected the dots quickly enough.

 _Jace_.

"Yes," Sebastian said and closed the door behind his back, making himself comfortable in the chair on the other side of Alec's desk. He'd heard him, then, and _that_ was a bit of a surprise - it had taken him and Jace quite a while before they'd managed to fully grasp the ability, but then again, they'd had no one to practice with but each other. If Jace had already prepared Sebastian for this, it was no wonder that he'd managed it so easily.

He wasn't sure when he'd noticed Sebastian's unending fascination with the parabatai bond. He had breached the topic with him much later than he had with Jace, which made sense – he and Jace had started getting closer earlier on because they'd clicked together rather quickly after their first meeting. They had too much in common for that _not_ to happen when they'd been given enough time and he'd started asking questions almost as soon as they'd come to the unspoken agreement that they could trust him with their secret.

In retrospect, Alec could see that ending up in their current situation had been almost inevitable – the process, slow as it had been, had started that day and they hadn't looked back ever since.

"We were talking about his magic and he mentioned that you're better at this than he is. And I thought-" Sebastian leant in further over the desk, voice lowering as he continued, "If you could do it on missions, it could work wonders. I don't mean during hunts," he clarified before Alec had had the chance to speak. "If you could communicate with someone else like this during Council meetings-"

Alec didn't need him to finish the suggestion to see the potential. It would be a challenge, that much he was sure of; so far, he and Jace had only attempted it when they were as close to each other as possible and the thought of doing it across the room in the presence of Clave representatives was more than a little unnerving. It wasn't that he thought that someone would suspect anything - the idea of parabatai breaking the law for a long enough time to reach such extremes was unfathomable to most Shadowhunters - but they'd spent so long trying to fly as low under the radar as they could that testing the limits of their bond in a place where everyone could see them made him feel almost greedy; as if they were _begging_ to get caught one way or another.

"You don't have to do it if you don't want to." Despite the reassurement, the enthusiasm in Sebastian's eyes hadn't diminished in the face of Alec's silence. _He's too persistent for his own good_ , that was what Alec had thought of him in the very beginning and while he had yet to be proved wrong, he found that - to his dismay - he'd started finding the quality endearing rather than threatening. "If you think it's too dangerous, then we don't have to even try it. You've had your meetings without telepathy before, after all."

The thing was, the idea was far too appealing for Alec to let it go now that Sebastian had mentioned it. During meetings with Clave officials and even representatives of the Downworld, especially when it came to the Seelies, there wasn't much that he could say to anyone without drawing too much attention to himself. There wasn't much that he could really change about the circumstances, telepathy or no telepathy; Jace was usually absent during meetings unless they were particularly important and more significant than any other assignment he had to deal with and Sebastian preferred to hover around the main entrance rather than to actually participate, but he would be close enough to hear if Alec signalled to him that something was wrong. It worked the other way around, too - Alec was well aware of the fact that the Head of the Institute being occupied usually provided the perfect excuse for all sorts of unsanctioned decisions to be made. The situation with Luke during the first Downworld Cabinet meeting was the perfect example and definitely not something that Alec would forget any time soon and that thought alone was enough for him to come to a decision.

"No one would even notice." Whether he was trying to convince Sebastian or himself, Alec wasn't sure and he didn't _need_ to be; at least not for now. Sebastian's eagerness was about as infectious as Jace's when it came to untried but daring plans and Alec found himself nodding despite his better judgement, Sebastian's widening smile made the worry he'd go through as soon as they put it into action worth it. "But we'll have to work on it first. We have to make sure that it works."

"Of course." Without any preamble whatsoever, Sebastian rose up from his chair and leant in over the desk for a kiss that Alec accepted readily despite their location. Even if they could handle the issue with the security footage – Sebastian had pulled quite a few tricks with it already to cover their tracks – it still wasn't a good idea to start anything in the heart of the Institute and he'd _said_ so enough times, but that didn't seem to stop Sebastian from going through with whatever it was that he wanted to do.

Sometimes Alec wondered if he actually knew what the risks were; if he'd ever considered the dangers of getting involved in the mess that he and Jace had created or if he'd just allowed himself to be swept along without a second thought. It didn't seem likely - he was too clever for that, as Alec had quickly realised - but it was still a possibility and if Alec had been a different person - someone far less selfish than he was - he would have pushed him away a long time ago. Hell, he would have persuaded Jace to do the same before things had had the chance to take a turn for the worse and before they dragged Sebastian down with them if - _when_ \- one of them slipped up and they were discovered.

As it was, though, he didn't have the heart to say anything and neither did anyone else. Both him and Jace kept their distance to the best of their abilities while they were in the Institute and at one point, without them even noticing, their attempts to be as inconspicuous as possible had started including Sebastian too. If he seemed far too close to either of them - or, as was the case, both of them - that would be enough to seem just a bit unusual and from then on, it was only a matter of time before the rumours started. Alec had seen it happen more than once; an otherwise respectable Shadowhunter's reputation being ruined because they'd been unable to keep their oddities behind closed door and whether they liked to think of that or not, the crime they were committing was much worse than most minor transgressions that the Clave was inclined to ignore. In that case, they wouldn't be the only ones to be prosecuted if word got out that Sebastian had been aware of what was happening and had actually been _involved_ in it.

Still, pushing the thought away way almost easy by now, made even easier by Sebastian's deepened kiss as his breathing hitched against Alec's lips and he adjusted his weight on top of the desk, fingers toying with the hem of Alec's shirt.

"I see the training's going well."

Sebastian pulled away immediately and sank back into his chair, eyes widening as he noticed Alec's complete lack of reaction at Jace's unceremonious entrance.

"You could feel him coming." It wasn't a question but Alec nodded anyway, oddly proud of the way Sebastian was looking between him and Jace. He seemed torn between his scientific curiosity and his ever present determination to not push further than they wanted him to and it wasn't exactly a _surprise_ that the former won. It usually did with him, and Alec was starting to get used to it.

"I told you, this is incredible." The words were directed at Jace and Alec narrowed his eyes as he watched Jace throw himself into the new direction of the conversation readily. They'd discussed this before, he could tell, and he could see that Jace was being far more understanding than he would have been usually. If it had been anyone else, he would have protested to being used as a guinea pig especially in the light of the more recent discoveries he'd made about himself, but this time around, he was actively _encouraging_ this. He was completely serious about it, too, and Alec could see it in his eyes despite the light-hearted smile he'd given as an answer to Sebastian's surprise. "But I'm not sure you can test it to its limits within the Institute walls."

"Of course we can't." Jace had taken it as a challenge, Alec noticed, and he wasn't as taken aback by this turn of events as he would have been if his bond with Jace had been a fraction weaker than it actually was. If anything, he'd seen it coming and he could feel Jace's excitement resonate within him too until he couldn't quite distinguish it from his own thoughts; all-consuming and yet completely natural. It had been that way for a while now and it hadn't occurred to him just how _different_ things had been before until Sebastian had pointed it out. "But if we're really going to do this..." For a moment, Jace's eyes flickered in Alec's direction and Alec nodded hastily. They couldn't hide from the new developments of their bond forever, and if they had someone to help them control it, it would be all the easier. It _had_ to be. "Then we could probably _start_ from here."

When Jace called his magic to the surface, Alec could almost feel it burning under his skin as well.


	2. Chapter 2

**Notes: Well, here it is, after approximately half a year. The supposed (not all that conclusive) conclusion of this fic. It's mostly character study, really, but that's what it started off as anyway, so I'm quite pleased with how it turned out. Hopefully it's enjoyable and I'd love to know what you guys think!**

"I can't do it, I'm sorry." Sebastian schooled his expression back into his usual encouraging smile with lightning speed, but not quickly enough for Jace to miss the flash of irritation across his features. "He's too far away," he snapped, frustrated with his own inability to do what he'd meant to. "We need to be closer to each other."

"You need to be closer," Sebastian repeated, running a hand through his hair, clearly in an effort to compose himself. "Jace, you won't always be close enough to help each other in battle. And if you can't help Alec, then what's the point of any of this?"

Truth be told, even though Jace was aware that he was trying, Sebastian wasn't the most patient teacher in the Shadow world. He didn't like it when anything took too long to work and he liked having to wait without doing anything even less and, to make things even worse, he seemed to have endless energy. Or, at the very least, enough to do this for hours on end without getting bored.

Jace, on the other hand, was _exhausted_. He could understand the importance of their work here – better than Sebastian himself did, most likely, even if he'd been the one to initiate it – but the constant pushing was far from the best method of encouragement out there.

"Of course I want to be able to help him," he said, doing his best to keep the exasperation away from his voice. "But it's not working. Not yet, anyway."

"It _will_ work," Sebastian said, taking Jace's hands into his own. "You just need to focus and I thought— maybe coming here wasn't a good idea."

"No," Jace hurried to protest. "It was an amazing idea. We would have never been able to do this back at the Institute."

He would have never been able to be as calm as he was here in the Institute. The possibility of being found out would be too great and there were only so many excuses that he could make before anyone who witnessed the things he and Alec were capable of would start being far too obvious.

So they'd come here. As far as Jace knew, Alec was still back at his office under the guise of working and was in fact testing his own abilities with a bit more success that Jace himself had had so far. It made sense – Alec was doing this in the safety of a place where no one would dare to question him as long as he looked focused enough, and he and Sebastian were in the middle of Central Park.

It was strange, to say the least, being here without visiting the Seelie Court or looking for a demon. They were out in broad daylight and neither of them had bothered with glamour – after all, the only people that would see something out of place in their presence could see through it anyway. As it was, Jace found himself feeling almost _mundane_ despite the work they'd come here to do. He knew that that was what everyone around saw when they looked at them – just an ordinary couple in an ordinary afternoon – and the thought was foreign enough to distract him from their _actual_ reason for being here once again.

"Think of it like this," Sebastian spoke again, his tone even more ambitious now. "You can feel it when Alec gets hurt, right?"

"Of course I can." The topic wasn't one he was too eager to delve in despite the fact that Sebastian was the one asking. He'd been able to feel him more easily recently and it wasn't necessarily a good thing - while it was always good to know when one's parabatai was in danger, both he and Alec had agreed that during the last few fights they'd got hurt in, the echo of the other's pain had always been intense enough to distract them from their mission. It wasn't an easy thing to admit, that the bond could be something to be wary of, but it was the truth nevertheless and it was all too easy for it to be ignored when it wasn't explicitly brought up. "As well as he can feel mine."

"Okay," Sebastian nodded, his eyes locking with Jace's with the same stubborn edge his gaze had had ever since this morning. "You know as well as I do that in times of war, not all fights happen at the same time and place. Imagine that one of you gets hurt while the other is too far away to get to him. What would you do then? You can't send him help. You can't heal him. All you can do is hope that there'll be someone else on his side there or - in case there isn't - wait for him to die. That's why we're doing this," he continued, tone pacifying as he squeezed Jace's hand, the gesture almost absent-minded. "You're stronger together than you are apart; we already know that. But if he can send you messages with his mind so that you're more effective in battle and you can heal him through your runes, you'll be _unstoppable_. You can't let something like that slip just because you're not sure if you can make it."

"You're right," Jace nodded. He didn't want to hear any more potential scenarios; not when he'd only managed to push the thought away from his mind for more than a minute. "Let's try again."

It wasn't just Sebastian's insistence, really. Jace had found his mind straying more and more to similar thoughts recently; the reasonable fear he'd had of losing his parabatai morphing into something much more intense. It was natural, Sebastian had told them when it had been brought up. It was yet another thing he'd read in his father's books: the closer two parabatai were, the more fixated they were on one another. He'd also assured them that it wouldn't get in the way during battle and that it would only aid them further but from where Jace was standing, it seemed more and more like a hindrance every time he decided to focus on it (which wasn't often; the thought was unpleasant enough that he'd purposefully started trying to pay no attention to it. If that was another thing to worry about, then he preferred not to dwell on it too much).

But now, here, Sebastian's smile was blinding and it was almost enough to make him forget his fears in the face of a promise of something that could hold them at bay. "Come on," he coaxed. "Close your eyes. Try to see Alec in your mind; call out to him like you do when you're trying to establish a telepathic connection. He's bound to feel it sooner or later."

Jace had never asked Sebastian where he'd learnt everything he knew about runes and he didn't plan on doing it now. The answer was rarely something pleasant and most often had to do with his father, which seemed to be the worst possible topic when it came to him. His knowledge had been nothing but useful so far, though, and he wasn't about to protest; not even when Sebastian's coaching got a little too much for him to deal with all at once.

Alec seemed to be taking it better. He'd taken to the new task with the same dedication he'd given to any of his studies during their childhood and so far, he'd been doing great with his part of the research they'd started doing on the bond. It had turned out that their ability to reach each other's mind when they wanted to wasn't affected by the distance between them and while they'd realised that the newly sharpened pain from the other's injuries had only started getting worse, they had found out something else too - the same went for the healing runes they used.

Which was what had led them to _this_. Jace's runes on Alec seemed to be more effective than vice versa and so he'd let himself be convinced that it was a good idea to try and activate Alec's runes through his own from an increasingly great distance. It had worked fine at first, but once they'd left the grounds of the Institute, it had stopped almost immediately and now, from the other end of the city, the task felt next to impossible.

Jace was resolute to make sure that it would work this time, though. Sebastian was right – the better he got at this, the safer both he and Alec would be and in the end, that was what they'd been aiming for from the start.

Correction - it was what _he_ had been aiming for. He wasn't sure whether the same went for Sebastian, who seemed more eager to use it as a weapon rather than a defence regardless of what he said and it wasn't difficult to see that he had bigger plans than just New York. In fact, it had been Jace who'd proposed this place and he dreaded to think what it would have been instead if he'd let him decide. For all his good intentions, Sebastian tended to be far too ambitious.

Jace could still feel his encouraging touch on his hand as he led the stele over his _true north_ rune. They'd picked it for the effect it had more than anything else - it was something that they were sure that Alec would feel, the sudden change of focus too intense to be ignored, and in case he did, he'd let them know immediately. It was a precarious arrangement, but they'd made it work and Jace focused all his energy into that one action, trying to picture the stele's magic flowing through their bond and into his parabatai. It certainly felt different this time around from what it had been like the other times he'd tried it – he could almost _see_ the connection, as if his and Alec's efforts to get closer to one another had finally managed to become tangible despite the space between them and all the obstacles in their way. _This was new_. New and addictive in a way he couldn't quite describe but couldn't get enough of either.

When he opened his eyes, Sebastian was grinning at him victoriously. He held his phone up for Jace to see the message that Alec had sent them and Jace felt himself smiling too, the sudden burst of pride making him feel far better than he had just a minute ago. He'd done it.

"You did a great job." Sebastian got to his feet and pulled him up. Jace followed in his tracks and only stopped when his boyfriend turned around for a kiss – one that he accepted eagerly. They'd agreed to go to lunch if this worked and Jace was definitely more than ready for that, the magic necessary for the trick he'd just performed too draining for him to wait until they got back to the Institute. "I knew you could do it," Sebastian added, not without a decent amount of pride, and after linking their hands together, led him down the hill.

After all the effort of the morning, the idea of lunch sounded heavenly and the diner they'd found for that purpose didn't disappoint. Jace wolfed down the meal he'd been given while Sebastian picked at his own food on the opposite site of the table, seemingly still enthralled by the progress they had achieved just today. He hadn't stopped texting Alec since then, likely questioning him about the things he'd felt during Jace's final, successful attempt at connection.

There was a reason why he and Isabelle spent so much time together, Jace thought. They both took an interest in the body that was more scientific than anything else and, tiring as the experiments could get sometimes, Jace still found it rather endearing. There was always something new he fiddled with and he was so enthusiastic about it that even things that would have worn out Jace's patience a long time ago - like the constant questions and displays of magic that he wanted, no matter how easy they were to achieve - had turned into something that he did without a second thought.

"What does Alec think about this?" Jace asked between two mouthfuls. "Can it work in battle?"

"He thinks yes," Sebastian said, still not looking up from the screen. "He also thinks that there's something else that could work, but we haven't perfected it yet."

That was another thing - the individual work he did with both of them. He was especially secretive about those particular ideas until something actually came out of them. He insisted that the effect would be stronger if the other wasn't aware that something was going to happen and even Alec, rather averse to surprises most of the time, had agreed. It felt almost like a _game_ sometimes - one that Jace didn't mind playing without caring where it would take them. He never knew what to expect and that made it feel even more like magic and drew him in even further; the constant awareness of how much the parabatai bond was changing and how much stronger they were becoming had swallowed up so much of his time and thoughts that it felt like the most important thing in his life. If Sebastian had been anyone else, he would have worried about him feeling left out, but as it were, he had definitely made a place for himself in their bond and Jace was more pleased with that than he had ever guessed he could be.

It was all in the little things he did to help them move further with their abilities, in the telepathic connection he could now achieve much more easily than the first time they had tried it together. In a way, Jace knew that they would have never got as far as they had if Sebastian hadn't been around to encourage it and the thought was both exciting and a little frightening; that something he and Alec had kept a secret for so long and with such painstaking care had morphed into something they shared with him like it was a given.

It was only when they had decided to leave - well after he had become wrapped up in his thoughts - that Jace noticed that something felt a little _off_.

"I think it would be better to ignore my own advice this time around," Sebastian started with a rather particular expression - one he usually saved for moments when he wanted to seem apologetic and also enthusiastic enough to lure one of them into whatever new scheme he'd thought of. Much to Jace's discontent, it worked without fail and Sebastian _knew_ that, so they saw it all too often. "Because what Alec's about to do - or what I _think_ he's about to do - goes a little further than our usual experiments."

"Did you have to do this _today_?" The incredulity in Jace's voice was enough to surprise him as well. He wasn't sure what _this_ was, but he suspected that he was about to find out in the very near future. "After everything we did this morning?"

"Alec thought that it might be a good idea." Sebastian had slowed his pace and Jace followed his example all too eagerly, his body feeling more and more foreign by the second. "If he can pull this off, he'll probably only need to do it when you're exhausted already and need someone else to take over."

"Take over," Jace repeated and he suspected that the exasperation creeping into his voice had become a little more obvious as the apologetic edge to Sebastian's general presence intensified. "Why does Alec always have to agree to the _worst_ possible—"

He trailed off as he stared at his hand with fascination mixed with horror, which then proceeded to spread to the rest of his body when his first instinct was to stop and see what was going on, only to have it _still walking_. It felt oddly like an invasion to see his legs move without his explicit permission, but he didn't do anything to stop it, more concerned with the mechanics of it happening at all. It stopped soon enough anyway, the foreign – _new_ , not foreign, because he knew exactly who the source was – force withdrawing as quickly as it had appeared and leaving him breathless in its wake.

 _We've gone too far._ He didn't say it, although it was the only logical conclusion. They had to draw a line somewhere and this seemed like the perfect moment, before they'd completely lost track of what was safe and what wasn't. But he couldn't find it in himself to protest; not when he could _feel_ the already familiar edges of Alec's magic settling inside his body, reaching him to the very core and it should have been alarming - this wasn't supposed to _happen_ , things like this were the reason they had been forbidden to want anything different from what they bond gave them - but it felt exhilarating instead and Jace leant against the nearest wall with whatever control he had left over his body, grateful when he felt Sebastian's arms wrap around him.

"This... this isn't like mind reading," he managed to say, closing his eyes at the maelstrom of sensation that reigned inside him.

"No, it isn't." Sebastian didn't sound properly worried yet, but it was close. "Is it too much? If you try, you can probably communicate that—"

"No, it's fine," Jace waved him off. "It's fine, just. Give me a moment." He opened his eyes again, trying to fight the sudden sensory overload – he had felt as if he was in Alec's office for a fleeting instant, and the complete silence in which his parabatai was working was in stark contrast to the streets of New York. "I can see how it can be useful. If I ever think I can't go on for whatever reason, Alec can just give me a hand. And if it's him being hurt, I can heal him with my runes. It's—" He didn't want to admit it since it was all still so _strange_ , but he had to. "It could work. I think it's going to work. How did you—"

"I told you." Sebastian's voice was smooth as silk and there was a moment of Jace feeling completely disoriented - he was in front of him, but he also wasn't in the room at all and Jace's confusion mixed with Alec's satisfaction at his success until he could no longer tell with absolute certainty where he was. If they were going to use this in the future, they would definitely have to work hard for it and even as the thought passed through his mind, Jace knew that they most definitely would - there was no way he could know that they could have this while also ignoring that knowledge because they'd had a rocky start. "Your strength is in the runes and Alec's is his mind. This could develop _beautifully_ if you let him - and me - in. It could save your life one day."

Jace thought about all the times in his life he had wished he could escape his life (his body) even for a little while. He thought about what was being offered to him; what they could _do_ , both in a battle and outside of it, if he'd just let himself have this, and he felt his resolve crumble bit by bit until there was nothing left.

"Yes," he said in the end, delirious and confused and almost ecstatic. "Show me."

Sebastian had finally climbed up on the bed and was leaning on his side, a small smile playing on his lips as he watched them. It was quite a sight, Jace imagined; Alec trailing a line of fervent kisses from his jawline all the way to his stomach, his hands still wrapped securely around Jace's shoulders as he lowered himself even more. They'd both noticed that physical contact felt different now that they'd tried this and even though they hadn't repeated the experiment again today - it was far too exhausting, they had found, and it wasn't like they didn't have enough time for perfecting it in the future - Jace still couldn't quite shake off the feeling it had left in him. Everything felt _sharper_ now, brand new and age old at the same time, and he couldn't get enough of it.

His soul had always been intertwined with Alec's, ever since they had said their vows, but this was different. He was an almost palpable presence inside Jace's body as well as his mind and it made him feel dizzy and overwhelmed and stronger than he had ever been. Each little step they made seemed to affect them differently, as Sebastian had pointed out, and Jace was inclined to agree. When it came to Alec, the changes in their bond had made him faster and more focused and, impossible as it sounded, even more efficient than he'd been before, while Jace just felt erratic - buzzing with energy and riding a constant high that made him itch for a fight at the slightest provocation. They had become far more dependent on each other than the Clave would deem advisable, _too_ dependent, a part of Jace's mind warned him, but it was an old, memorised caution; one that he felt almost ready to let go of.

It was nothing but his father's lessons raising their ugly heads yet again, he could tell that much. The talk about how the only person you could safely depend on was yourself was a well-familiar one but definitely not applicable to the current reality of his life. This was _Alec_ , his parabatai – he could rely on him as much as he could rely on himself, and Sebastian had done nothing but help enhance that further. Content with the thought, Jace reached out blindly to draw him near and grinned when he felt fingers wrapping around his own, a second body pressing against them as Sebastian leant in to kiss him. Any risk he could take was worth it for _this_. They would make it work one way or another, he was sure of it, and nothing his father had ever said would be able to take that away from him.


End file.
